Stabilization of Fatty Oils and Esters with Alkyl Phenol Amine Aldehyde Condensates

ABSTRACT

Biodiesel fuels, renewable diesel fuels and feedstocks to these fuels (derived from plant seed oils or animal fats) are viewed as more environmentally friendly, renewable alternative fuels or supplemental fuels with petroleum-based diesel. Alkyl phenol amine aldehyde condensates improve the stability of biofuels by inhibiting the degradation processes. Alkyl phenylene diamines employed together with alkyl phenol amine aldehyde condensates in the biofuels give synergistically improved stability of the fuels.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/991,406 filed on Nov. 30, 2007.

TECHNICAL FIELD

The present invention relates to methods and compositions for improvingbiofuels (including biodiesel fuels, renewable diesel fuels, and relatedfeedstocks) and more particularly to the use of alkyl phenol aminealdehyde condensates alone or together with alkyl phenylene diamines toimprove biodiesel fuels by extending their oxidative stability and, inturn, inhibiting residue formation and discoloration.

TECHNICAL BACKGROUND

It is well known that as the cost of crude oil increases, numerousefforts have been made to find and develop alternative fuels,particularly fuels that have a renewable, rather than a limited, source.Considerable effort has been expended researching potential fuels fromregenerable biological sources, or biofuels. Biofuels, in the contextherein, include biodiesel and renewable diesel, which are dieselfuel-equivalents, processed fuel derived from biological sourcefeedstocks (such as plant seed oils, vegetable oils and animal fats),and which may be used in unmodified diesel engine vehicles. Such fuelsare viewed as more environmentally friendly, renewable alternative orsupplement fuels to and with conventional petroleum-based diesel.Biofuels are also seen as having the advantage of reducing dependence onforeign-sourced petroleum based oil. Characteristically, the biodieselhas a high flash point for safe handling, has good lubricity, isbiodegradable, has reduced emissions (lower particulate matter, carbonoxides and unburned hydrocarbons), and its use fits with existinginfrastructure. Alternatively, the renewable diesel is not hygroscopic,has improved cold flow properties for low-temperature handling, hasreduced emissions, has higher cetane values to improve the combustionquality, and its use also fits with existing infrastructure.

In the context herein, biodiesel fuels include, but are not necessarilylimited to, alkyl esters of a fatty acid, typically either the ethylester or methyl ester of a fatty acid. Thus, many biodiesel fuels may beunderstood to contain fatty acid methyl esters (FAME). The FAMEs orblends thereof are typically referred to as biodiesel. For instance,blends of FAME with No. 2 fuel oil may be referred to as biodiesel. Mostbiodiesel fuel is presently made by the transesterification of fattyacids. Biodiesel fuel may also be made from free fatty acids using anacid catalyst. There are other processes that use an ion-exchange resincatalyst.

In more detail, most biodiesel fuels are made from vegetable oils,including, but not necessarily limited to rapeseed, soybean, cottonseed, corn, jotropha and the like oils. Some biodiesel is made fromanimal fats, including, but not limited to beef and pig tallow, chickenfat, fry grease, restaurant trap grease, fish oil, and the like. Effortsare also being made to blend FAME compounds to modify properties such aslow temperature handling, for instance esters from palm and soybean oilsor soybean and tallow oils (e.g. beef). The mixtures may be complex. Allof these fall within the definition of biofuels herein.

Non-esterified or straight vegetable oils (SVO) or straight wastevegetable oil (WVO) are examples of typical biomass feedstocks for theproduction of biodiesel or renewable diesel. However, biodiesel andrenewable diesel fuels as defined herein may include thesenon-esterified SVOs or WVOs in minor proportions (less than 50 volume %,and in another embodiment less than about 1%). In the context herein,renewable diesel fuels include, but are not necessarily limited to, thehydrocarbon products resulting from the reactions of plant or animaloils under various conditions, not to include esterification. In moredetail, renewable diesel fuels can be prepared from the directhydrotreating of the plant or animal oil feedstocks, through theFischer-Tropsch process (coal-to-liquid or gas-to-liquid catalyzedreactions), direct pyrolysis of biomass, or through an algae (or otherbiological organism) production system. As with biodiesel, efforts arebeing made to blend renewable diesel with petroleum-based fuels tomodify properties such as decreased emissions. The mixtures may becomplex. All of these fall within the definition of biofuels herein.

The biodiesel fuel B100 has a particular definition, including, amongother parameters, a minimum ester content of 96.5 wt %. It may be madeby transesterifying triglycerides from plant or animal-based fatty acidoils with alcohol in the presence of a catalyst.

Biofuel instability occurs due to higher levels of unsaturatedcompounds, which are sites for oxidation reaction over time, and whichare accelerated at elevated temperatures and by the presence ofcontaminants including metals and sulfides. This instability due tooxidative degradation is greater than that associated with conventionalpetroleum diesel. During transportation and storage, biofuel may besubjected to conditions that promote oxidation of their unsaturatedcomponents subsequently degrading quality and performance withundesirable characteristics of residue, acidity, odor and discoloration.

There is a need to improve the stability of biofuels and feedstocks. Itis desirable to discover a method and/or composition for improving thestability of biofuel, feedstocks and biofuel blends.

SUMMARY

There is provided, in one non-limiting embodiment a method for improvingthe stability of a biofuel, comprising adding to the biofuel an alkylphenol amine aldehyde condensate additive in an amount effective toimprove the stability thereof. Optionally, an alkyl phenylene diaminemay also be employed.

Further, there is provided in another non-restrictive version animproved biofuel that contains fatty acid methyl esters, hydrocarbons,or oils and an alkyl phenol amine aldehyde condensates in an amounteffective to improve the stability of the fuel. Again, optionally, analkyl phenylene diamine may also be employed.

DETAILED DESCRIPTION

In accordance with the present invention, it has been unexpectedlydiscovered that certain alkyl phenol amine aldehyde condensates, such asdodecyl phenol polyamine formaldehyde Mannich base, are surprisinglyeffective at improving the stability of biofuels. These additivesprotect the biofuel by inhibiting the degradation process. The storagestability of the biofuel is extended and the end-use quality isimproved.

In another non-limiting embodiment, it has also been unexpectedlydiscovered that the alkyl phenol amine aldehyde condensates usedtogether with alkyl phenylene diamine-type chemistries form asynergistic blend to stabilize these mono-alkyl esters of long-chainfatty acids, typically FAME, and mixtures thereof with conventional No.2 fuel oil commonly referred to as biodiesel. This combination alsoinhibits the oxidation process and protects against product degradation,extending the FAME/biofuel storage stability to improve end-use quality.

The exact mechanism by which the methods herein operate is not known,and thus the inventors herein do not wish to be limited by anyparticular explanation. The treatment with these additives has at leastthe effect of increasing the oxidative stability of the biofuel. Thestability of the biofuel is improved as compared with a biofuel absentthe additive. Improving the biofuels by this method is relatively moreeconomical compared to some alternative methods.

The alkyl phenol amine aldehyde condensate may have the general formula:

where R₁ are independently straight or branched alkyl groups of C₁-C₂₀and may be located at the ortho, meta or para positions, alternativelyof C₄ to C₁₆, where x ranges from 1 to 5. The condensates of generalformula (I) may be made by reacting an alkyl phenol with an aldehyde(e.g. formaldehyde) and a polyamine (e.g. ethylenediamine), such asschematically illustrated below:

where R₁ is as defined above. Representative, non-limiting examples forR₁ are butyl, amyl, nonyl, dodecyl, and the like. Specific examples ofsuitable alkyl phenol amine aldehyde condensates include, but are notnecessarily limited to, dodecyl phenol ethylenediamine formaldehydeMannich base, nonyl phenol diamine formaldehyde Mannich base, amylphenol diamine formaldehyde Mannich base, and butyl phenol diamineformaldehyde Mannich base.

Suitable polyamine reactants may have the general formulaH₂N—(CH₂CH₂NH)_(x)—H where x ranges from 1 to 5; and in an alternateembodiment, x ranges from 1 to 3. Suitable diamine reactants include,but are not necessarily limited to, ethylene diamine, diethylenetriamine, triethylene tetramine, and the like.

While it is expected that formaldehyde will be the most likely aldehydeused to make the condensates of general formula (I), other aldehydessuch as acetaldehyde, propionaldehyde and the like may also be used.

In general, the mole ratio of reactants to make the condensates ofgeneral formula (I) will be about 1 mole of polyamine to about 2 molesaldehyde to about 2 moles alkylphenol, however the ratio may also beabout 1 mole polyamine to about 2 moles aldehyde to about 1 molealkylphenol. The reaction conditions are generally such that the mixtureof alkylphenol, polyamine and aldehyde are present in a solvent,typically an aromatic solvent, which is heated to reflux and water isremoved. The reaction is considered complete once water is no longercoming off the reaction.

In one non-limiting embodiment, the amount of alkyl phenol aminealdehyde condensate employed as an additive in the biofuel to improveits stability ranges from about 10 to about 10,000 ppm, based on thebiofuel. Alternatively, the amount of alkyl phenol amine aldehydecondensate may have a lower threshold of about 100 ppm, andindependently an upper threshold of about 2000 ppm.

The alkyl phenylene diamines useful as oxidative stabilizers in themethods and compositions herein may have the general formula:

where R₂ are independently straight or branched alkyl groups of C₁-C₂₀,alternatively of C₄ to C₁₆. The diamines may be in the para, ortho ormeta position with respect to one another. Suitable alkyl phenylenediamines include, but are not necessarily limited to,N,N′-di-sec-butyl-p-phenylenediamine,N,N′-di-iso-butyl-p-phenylenediamine, andN,N′-di-iso-propyl-p-phenylenediamine.

In one non-limiting embodiment, the amount of alkyl phenol aminealdehyde condensate and alkyl phenylene diamine in the non-restrictiveembodiment when both are employed as additives in the biofuel to improveits stability ranges from about 10 to about 10,000 ppm, based on thebiofuel. Alternatively, the amount of alkyl phenol amine aldehydecondensate may have a lower threshold of about 50 ppm, and independentlyan upper threshold of about 1500 ppm.

The resulting additive, be it alkyl phenol amine aldehyde condensatealone or together with an alkyl phenylene diamine, may be added to thebiofuel to be treated by standard techniques, such as by injection orsimple pouring and it may be dispersed throughout the fuel by stirringor other agitation. The additive is incorporated at a level sufficientto improve the fuel stability. In practice, one would dose test bottleswith varying amounts of the additive to determine how much is requiredto give the desired stability.

The biodiesel containing FAME may be any biofuel as previously defined.The biofuels may contain other oxygenated compounds besides esters, suchas alcohols, glycols, ethers and the like and mixtures thereof.

Effective treatment may be carried out at the ambient temperature of thebiofuel (e.g., about 20° C. for stored fuel), but the performance of theadditive is expected to be effective at typical storage and handling aswell as engine operating temperatures (e.g., about 20° C. to 200° C.).Thus, the additive may still be employed at such elevated temperatureswith good results.

In one non-restrictive version, the oxidative stability of a biofuel ismeasured using the Rancimat Test EN14112, which is a test thataccelerates oxidation of the fuel. This biofuel stability test methodgenerally involves measuring the induction time for volatile oxidationproduct formation in hours as related to resistance to oxidation oroxidation reserve, or the time to the start of deposit formation. Inmore detail, this test involves passing air through a sample of thebiofuel at an elevated temperature. As oxidation occurs, volatileoxidation products are formed which are swept from the sample andcollected in a downstream cell. The conductivity of the solution in thecell is monitored during the test. It is determined when enoughoxidation of the biofuel has occurred that sufficient volatile oxidationproducts are formed and swept from the sample to cause a spike inconductivity of the cell. The method takes the maximum second derivativeof the conductivity curve as the induction period. The longer that thesample can be heated/sparged with air before this spike in volatileoxidation products formation occurs, the more stable the biofuel is.

Stability is a concern with biofuel storage. As noted previously, manyof the feedstocks for the biofuels are oils like rapeseed or soybeanoils. The fatty acid chains in these oils contain unsaturation (oleic,linoleic, linolenic etc.) which is subject to oxidation. It does nottake much unsaturation in the oils to be a potential problem. Stabilityis important because the unsaturation tends to discolor and eventuallyform solids (gums) as a result of oxidation during storage. Thepotential solids/discoloration of the biofuels makes them lessattractive as a fuel to an end user and can potentially cause engineissues such as filter or injector fouling.

Other commonly used, optional components in biofuels and biofuel blends(e.g., B2, B5, B20) include, but are not necessarily limited to,detergents, antiwear agents, demulsifiers, corrosion inhibitors, metaldeactivators, cold flow improvers, antifoams and biocides.

The following examples describe certain specific embodiments of theinvention. Other embodiments within the scope of the claims herein willbe apparent to one skilled in the art from consideration of thespecification or practice of the methods as disclosed herein. It isintended that the specification, together with the examples, beconsidered exemplary only, with the scope and spirit of the inventionbeing indicated by the claims which follow the examples. In theexamples, all percentages are given on a weight basis unless otherwiseindicated.

Experimental

The Rancimat stability tests were conducted on nine differentplant-derived B100 biofuels. The various additives used are identifiedin Table I.

TABLE I Oxidative Stability Additives Experimental designation IdentityY7BH1018 Dodecyl phenol ethylenediamine formaldehyde Mannich baseY7BH1100 Nonyl phenol ethylenediamine formaldehyde Mannich base Y7BH1019N,N′-di-sec-butyl-p-phenylenediamine Y7BH1068 92.5% to 7.5% blend ofnonyl phenol ethylenediamine formaldehyde Mannich base toN,N′-di-sec-butyl-p- phenylenediamine Y7BH1099 80% to 20% blend of nonylphenol ethylenediamine formaldehyde Mannich base to N,N′-di-sec-butyl-p-phenylenediamine

Examples 1-42 were conducted where an alkyl phenol amine aldehydecondensate was used as the only antioxidant additive.

TABLE II Rancimat Results Ex. Fuel 1878-119-7 1 Blank 0.2 hr 2 1150 ppmY7BH1100 6.3 hr 3 1200 ppm Y7BH1100 6.5 hr 4 1500 ppm Y7BH1100 7.1 hr 52000 ppm Y7BH1100 8.0 hr 6 2000 ppm Y7BH1018 6.3 hr

TABLE III Rancimat Results Ex. Fuel 1878-119-6 7 Blank 3.2 hr 8 500 ppmY7BH1018 9.4 hr 9 500 ppm Y7BH1100 10.3 hr 

TABLE IV Rancimat Results Ex. Fuel 1878-119-5 10 Blank  6.5 hr 11 500ppm Y7BH1018 14.3 hr 12 500 ppm Y7BH1100 15.8 hr

TABLE V Rancimat Results Ex. Fuel 1878-118-8 13 Blank  9.4 hr 14  500ppm Y7BH1018 15.7 hr 15 1000 ppm Y7BH1018 18.4 hr 16 1500 ppm Y7BH101821.1 hr

TABLE VI Rancimat Results Ex. Fuel 1878-118-6 17 Blank 4.2 hr 18  500ppm Y7BH1018 5.3 hr 19 1000 ppm Y7BH1018 6.1 hr 20 1200 ppm Y7BH1018 6.4hr 21 1500 ppm Y7BH1018 6.9 hr 22 2000 ppm Y7BH1018 7.3 hr

TABLE VII Rancimat Results Ex. Fuel 1878-118-9 23 Blank 4.5 hr 24  250ppm Y7BH1018 6.2 hr 25  500 ppm Y7BH1018 6.6 hr 26 1000 ppm Y7BH1018 7.5hr 27 1500 ppm Y7BH1018 8.7 hr

TABLE VIII Rancimat Results Ex. Fuel 1878-117-1 28 Blank 3.1 hr 29  500ppm Y7BH1018 4.2 hr 30 1000 ppm Y7BH1018 7.8 hr

TABLE IX Rancimat Results Ex. Fuel 1878-118-3 31 Blank 6.5 hr 32 500 ppmY7BH1018 7.7 hr 33 1000 ppm Y7BH1018 9.5 hr 34 2000 ppm Y7BH1018 10.2hr 

TABLE X Rancimat Results Ex. Fuel 1878-118-4 35 Blank 4.2 hr 36 1000 ppmY7BH1018 6.4 hr 37 1500 ppm Y7BH1018 7.5 hr 38 2000 ppm Y7BH1018 8.0 hr

TABLE XI Rancimat Results Ex. Fuel 1878-118-7 39 Blank 3.5 hr 40 1000ppm Y7BH1018 5.3 hr 41 2000 ppm Y7BH1018 7.4 hr 42 2500 ppm Y7BH1018 8.4hr

It may be seen from the results in Tables II-XI that alkyl phenol aminealdehyde condensates used alone consistently improve the oxidativestability of a wide variety of biofuels as measured by the Rancimattest, and dramatically improved the stability of certain biofuels,notably those of Tables III and IV. In all cases, increased amounts ofadditive increased the Rancimat test result; note particularly TablesII, V, VI, VII, VIII, IX, X and XI.

Tables XII-XIV next present the Rancimat test results for both additiveswhere only an alkyl phenol amine aldehyde condensate, only an alkylphenylene diamine, and also blends where an alkyl phenol amine aldehydecondensate together with an alkyl phenylene diamine are used. Forclarity, the blends are denoted; alkyl phenol amine aldehyde condensateis abbreviated APAAC and alkyl phenylene diamine is abbreviated APDA. Itmay be seen that the blends give consistently better results than theindividual components alone when used at the same dosage levelsindicating synergistic results. This is particularly evident in TablesXII and XIII where the same total amounts of additives are used.

TABLE XII Rancimat Results Ex. Fuel 1878-118-8 Type 43 Blank —  8.6 hr44 500 ppm Y7BH1019 APDA 13.8 hr 45 500 ppm Y7BH1018 APAAC 15.8 hr 46500 ppm Y7BH1068 Blend 17.1 hr

TABLE XIII Rancimat Results Ex. Fuel 1878-119-5 Type 47 Blank —  6.5 hr48 500 ppm Y7BH1019 APDA 12.7 hr 49 500 ppm Y7BH1018 APAAC 14.3 hr 50500 ppm Y7BH1068 Blend 15.8 hr

TABLE XIV Rancimat Results Ex. Fuel 1878-119-7 Type 51 Blank — 0.2 hr 52 750 ppm Y7BH1019 APDA 1.8 hr 53 2000 ppm Y7BH1018 APAAC 6.3 hr 54 1200ppm Y7BH1100 APAAC 6.5 hr 55 1500 ppm Y7BH1100 APAAC 7.1 hr 56  850 ppmY7BH1068 Blend 6.5 hr 57 1000 ppm Y7BH1068 Blend 7.1 hr 58  500 ppmY7BH1099 Blend 6.0 hr 59  850 ppm Y7BH1099 Blend 7.3 hr

The majority of the previous data was collected using Soy Methyl Ester(SME) biodiesel. The data collected in Tables XV and XIX was by usingRape-seed Methyl Ester (RME) biodiesel.

TABLE XV Rancimat Results Ex. Fuel RME #1 60 Blank 3.6 hr 61 500 ppmY7BH1100 7.6 hr 62 500 ppm Y7BH1099 8.8 hr 63 500 ppm Y7BH1018 6.9 hr

TABLE XVI Rancimat Results Ex. Fuel RME #2 64 Blank 3.4 hr 65 500 ppmY7BH1100 7.0 hr 66 100 ppm Y7BH1099 5.2 hr 67 250 ppm Y7BH1099 6.7 hr 68400 ppm Y7BH1099 7.6 hr 69 500 ppm Y7BH1099 8.2 hr 70 750 ppm Y7BH10999.4 hr

TABLE XVII Rancimat Results Ex. Fuel RME #3 71 Blank 3.8 hr 72  250 ppmY7BH1099 5.5 hr 73  500 ppm Y7BH1099 6.6 hr 74 1000 ppm Y7BH1099 8.5 hr75  250 ppm Y7BH1100 4.7 hr 76  500 ppm Y7BH1100 5.4 hr 77 1000 ppmY7BH1100 6.8 hr

TABLE XVIII Rancimat Results Ex. Fuel RME #4 78 Blank 1.3 hr 79  250 ppmY7BH1018 2.2 hr 80  500 ppm Y7BH1018 2.9 hr 81 1000 ppm Y7BH1018 3.0 hr

TABLE XIX Rancimat Results Ex. Fuel 1878-119-1 82 Blank 2.9 hr 83 250ppm Y7BH1099 8.5 hr 84 500 ppm Y7BH1099 9.9 hr 85 750 ppm Y7BH1099 10.4hr  86 250 ppm Y7BH1100 7.6 hr 87 500 ppm Y7BH1100 8.4 hr 88 750 ppmY7BH1100 9.0 hr

In the foregoing specification, the invention has been described withreference to specific embodiments thereof. It has been demonstrated aseffective in providing methods and compositions for improving biofuels,particularly increasing oxidative stability. However, it will be evidentthat various modifications and changes can be made thereto withoutdeparting from the broader spirit or scope of the invention as set forthin the appended claims. Accordingly, the specification is to be regardedin an illustrative rather than a restrictive sense. For example,specific combinations of alkyl phenylene diamines, alkyl phenol aminealdehyde condensates, biofuels, and other components falling within theclaimed parameters, but not specifically identified or tried in aparticular composition or under specific conditions, are anticipated tobe within the scope of this invention.

As used herein, the word “comprising” as used throughout the claims isto be interpreted to mean “including but not limited to”.

The present invention may suitably comprise, consist or consistessentially of the elements disclosed and may be practiced in theabsence of an element not disclosed.

1. A method for improving the stability of a biofuel comprising addingto the biofuel an alkyl phenol amine aldehyde condensate additive in anamount effective to improve the stability thereof.
 2. The method ofclaim 1 where the alkyl phenol amine aldehyde condensate has the generalformula:

where the R₁ groups are independently straight or branched alkyl groupsof C₁-C₂₀, and where x ranges from 1 to
 5. 3. The method of claim 1where the additive is added to the biofuel in an amount from about 10 toabout 10,000 ppm, based on the biodiesel fuel.
 4. The method of claim 1further comprising adding to the biofuel an alkyl phenylene diamine inan amount effective to improve the stability thereof.
 5. The method ofclaim 4 where the alkyl phenylene diamine has the general formula:

where the R₂ groups are independently straight or branched alkyl groupsof C₁-C₂₀.
 6. The method of claim 5 where the alkyl phenylene diamine isadded to the biofuel in an amount from about 10 to about 10,000 ppm,based on the biofuel.
 7. A method for improving a biofuel, comprisingadding to the biofuel an additive composition comprising an alkyl phenolamine aldehyde condensate and an alkyl phenylene diamine, where eachcomponent is present in an amount from about 10 to about 10,000 ppmbased on the biofuel.
 8. The method of claim 7 where the alkyl phenolamine aldehyde condensate has the general formula:

where the R₁ groups are independently straight or branched alkyl groupsof C₁-C₂₀, and where x ranges from 1 to
 5. 9. The method of claim 7where the alkyl phenylene diamine has the general formula:

where the R₂ groups are independently straight or branched alkyl groupsof C₁-C₂₀.
 10. A biofuel comprising: combustible hydrocarbons comprisinghydrocarbons from biological source feedstocks; and an alkyl phenolamine aldehyde condensate additive in an amount effective to improve thestability of the fuel.
 11. The biofuel of claim 10 where the additive ispresent in an amount about 10 to about 10,000 ppm, based on the biofuel.12. The biofuel of claim 10 where the alkyl phenol amine aldehydecondensate has the general formula:

where the R₁ groups are independently straight or branched alkyl groupsof C₁-C₂₀, and where x ranges from 1 to
 5. 13. The biofuel of claim 10where the additive further comprises an alkyl phenylene diamine in anamount effective to improve the stability thereof.
 14. The biofuel ofclaim 13 where the alkyl phenylene diamine has the general formula:

where the R₂ groups are independently straight or branched alkyl groupsof C₁-C₂₀.
 15. The biofuel of claim 10 where the alkyl phenylene diamineis present in the biofuel in an amount from about 10 to about 10,000ppm.
 16. A biofuel comprising: combustible hydrocarbons from biologicalsource feedstocks; from about 10 to about 10,000 ppm based on thebiodiesel fuel of an alkyl phenol amine aldehyde condensate; and fromabout 10 to about 10,000 ppm based on the biodiesel fuel of an alkylphenylene diamine.
 17. The biofuel of claim 16 where the alkyl phenolamine aldehyde condensate has the general formula:

where the R₁ groups are independently straight or branched alkyl groupsof C₁-C₂₀, and where x ranges from 1 to
 5. 18. The biofuel of claim 16where the alkyl phenylene diamine has the general formula:

where the R₂ groups are independently straight or branched alkyl groupsof C₁-C₂₀.